1. Field of the Invention
The present invention relates to improvement of a microscope provided with an objective lens focusing apparatus and an objective lens switching apparatus, and more particularly to improvement of an objective lens focusing apparatus which moves an objective lens or a stage in the microscope and an objective lens switching apparatus which is employed in the same microscope and provides such a function as magnification switching.
2. Description of the Related Art
Generally, the microscope includes an objective lens focusing apparatus for moving an objective lens to focus on a specimen and an objective lens switching apparatus for switching a plurality of the objective lenses to place one of them selectively on an observation optical axis.
As the focusing mechanism, there are two types, namely one type in which the objective lens is moved upward or downward (hereinafter referred to as up/down) along the optical axis and another type in which a stage supporting a specimen is moved up/down, in order to adjust a distance between the specimen and the objective lens or the stage. Generally, the focusing apparatus is provided with a rough motion handle and a fine motion handle. In this focusing apparatus, if the rough motion handle is rotated, a rotation of this rough motion handle is transmitted to a rough motion shaft, and further the rotation is transmitted to a pinion and rack and transformed to a vertical motion. Consequently, the objective lens is moved in rough motion in any one of the vertical directions along a guide.
If the fine operation handle is rotated, a rotation of the fine motion handle is decelerated by a reduction gear or the like and transmitted to the rough motion shaft. This rotation is transmitted to the pinion and rack gears and transformed to a vertical motion, so that the objective lens is moved in fine motion in any one of the vertical directions along the guide.
Therefore, even if the rough motion handle and the fine motion handle are rotated by the same rotation amount or by the same rotation number, the moving amount of the objective lens due to the operation of the rough motion handle is larger than the moving amount of the objective lens due to the operation of the fine motion handle. When the rough motion handle is operated, the objective lens is moved in rough motion, while when the fine motion handle is operated, the objective lens is moved in fine motion.
The rough/fine motion handle of the focusing apparatus is provided on a bottom side thereof, away from the front side or from the stage as viewed from an observer. The reason why the rough/fine motion handle is disposed in such a way is that a guide for moving the objective lens or the stage vertically is located at a rear side of the stage and the rough/fine motion handle is directly and mechanically coupled to the guide. Usually, an arm for holding the objective lens or the stage is fixed on this guide in a cantilever form.
If the rough/fine motion handle is disposed on the bottom side away from the stage as viewed from the front side of the microscope main body, in case where various devices are disposed around the stage to observe the specimen as seen in, for example, patch clamp method or in case where the eye position of the observer is raised depending on microscope system, the operability of the rough/fine motion handle is deteriorated considerably, which is a problem demanded to be solved.
An example of technology, which has improved the operability of the rough/fine motion handle, is a microscope focusing apparatus described in Jpn. Pat. Appln. KOKAI Publication No. 6-222276. FIG. 1 shows a microscope provided with this microscope focusing apparatus. The microscope shown in FIG. 1 includes a microscope frame 201 comprised of a horizontal arm portion 201A, a base portion 201B and a vertical portion 201C. A light source 202 is provided on the base portion 201B of the microscope frame 201 and the horizontal arm portion 201A has an objective lens 203, a lens tube 204 and an ocular lens 205.
A fixing base 206 is provided on the vertical portion 201C of the microscope frame 201 and a moving base 208 is provided on this fixing base 206 through a guide 207 such that it is movable vertically. A stage holder 209 is supported by this moving base 208 in a cantilever form. A stage 211 for supporting a specimen 210 is provided on this stage holder 209 and a condenser lens 212 is provided below it.
An operation handle 213 for moving the stage 211 vertically is supported rotatably on the base portion 201B, for example, of the microscope frame 201. This operation handle 213 has a transmission mechanism of the following structure. The operation handle 213 is connected to a longitudinal base 216 through a pinion gear 214 and a horizontal rack gear 215. This longitudinal base 216 is placed on a fixing plate 218 through a guide 217. A horizontal rack 219 is provided on the longitudinal base 216, with which an idler 220 meshes. This idler 220 is provided on the moving base 208 and meshes with a vertical rack 221.
Therefore, if the operation handle 213 is operated, a rotation of this operation handle 213 is transformed to a motion in the back and forth direction of the longitudinal base 216 through the pinion 214 and the horizontal rack 215, and the motion of this longitudinal base 216 is transformed to a vertical motion of the vertical rack 221 through the horizontal rack 219 and the idler 220. Because the moving base 208 is moved vertically for the reason, the stage 211 is moved vertically.
However, because in the above described microscope focusing apparatus, the longitudinal base 216 is connected to the operation handle 213 through the pinion 214 and the horizontal rack 215 and the horizontal rack 219 and the idler 220 mesh with this longitudinal base 216 while connected to the moving base 208 through the vertical rack 221, the structure of that transmission mechanism is complicated. Consequently, because there are a number of mechanical connecting portions, there is a fear that looseness may occur thereby transmission accuracy being not sufficient. Further, this transmission mechanism takes much time and labor for assembly and adjustment and induces an increased cost.
Further, an objective lens switching apparatus, in which one of plural objective lenses 305 is switched selectively onto the observation optical axis as shown in FIGS. 2 to 7 has been already known.
In a transmission illumination type optical microscope shown in FIG. 2, a revolver 306 holding plural objective lenses 305 as well as an ocular lens-barrel 304 are mounted on an end of the objective arm 303 which is arranged substantially in parallel to the stage 302 of the microscope main body 301. By rotating this revolver 306, one objective lens is switched selectively from plural objective lenses 305 onto the observation optical axis.
The revolver 306 shown in FIG. 2 comprises a revolver main body 306A shown in FIG. 3 and a turning ring 306B. Plural objective lenses 305 are held by the turning ring 306B along the circumference of the turning ring 306B. A pressing ring 307 is inserted on the side of the turning ring 306B between a peripheral portion of the revolver main body 306A and the turning ring 306B. This pressing ring 307 is fit to an outer edge portion of the revolver main body 306A through balls 308. Further, a ball 309 is held at the rotation center between the revolver main body 306A and the turning ring 306B and this ball 309 is pressed at a predetermined force by a pressing screw 310 driven from a rear side of the revolver main body 306A. Thus, the turning ring 306B is rotated smoothly without any swivel with respect to the revolver main body 306A via the balls 308, 309.
As shown in FIG. 4, the proximal end of a click spring 311 having a click ball 312 at a front end thereof is fixed on the revolver main body 306A. On the other hand, a click groove 313 is formed in the periphery portion of the turning ring 306B corresponding to a mounting position of the objective lens 305. If the turning ring 306B is rotated so that the objective lens 305 comes near the optical axis, the click ball 312 located at the front end of the click spring 311 drops into the click groove 313. As a result, the turning ring 306B is fixed without any swivel by the pressing force of the click spring 311, so that the objective lens 305 is positioned on the optical axis.
Recently, a manipulator has been combined with the optical microscope in order to not only observe a cell but also carry out various kinds of cell operations such as gripping, piercing, injection and cutting.
FIG. 5 shows schematically the microscope system using such a manipulator. As shown in FIG. 5, an objective lens 318 and a manipulator 319, held by the revolver 317, are disposed such that they are adjacent a specimen 316 placed on the stage 315 of the microscope main body 314. This microscope system enables not only to operate the manipulator 319 to the specimen 316 but also observe a specimen image through the objective lens 318. In this system, a controller 320 is connected to the manipulator 319 and rotations of dials 321A, 321B provided on this controller 320 are transformed to fine motion of the manipulator 319. Therefore, the manipulator 319 can be operated finely.
In case of changing the observation magnification of the specimen image in such a specimen observation, the revolver 317 is rotated so as to switch the objective lens 318. If it is intended to rotate the revolver 317 without any treatment upon this switching, there is generated such a problem that the manipulator becomes an obstacle, thereby disabling the revolver from being rotated or the objective lens 318 comes into contact with part of the manipulator 319 during the rotation of the revolver 317, so that a front end of the manipulator 319 deflects.
In the positioning mechanism shown in FIG. 4, at an engagement time when the click ball 312 drops into the click groove 313 in order to obtain a restoration force for positioning, a pressing force is applied from the click spring 311 to the click groove 313 in the turning ring 306B. Therefore, a relatively large impact occurs when the click ball 312 drops into the click groove 313 and the front end of the manipulator 319 is vibrated by this impact, so that the manipulator may be slipped out of a cell being handled.
From such a background, an objective lens replacing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 6-40910 has been proposed conventionally.
In this apparatus, as shown in FIGS. 6 and 7, two objective lenses OB1, OB2 are installed on a lens switching member 331 movably in a circular shape along the direction of the arrangement. This lens switching member 331 is supported rotatably on a fixing member 332 with a ball 333 and ball receivers 334, 335. A positioning shaft 336 including multiple thread screw formed therein is driven into a screw hole formed in a side face of the lens switching member 331. This positioning shaft 336 is driven by operating the lever 337, so that a positioning ball 338B provided on a side face of the fixing member 332 is fit to a conical concave portion at a front end of the positioning shaft 336 so as to position the objective lens OB1. When replacing the objective lens, the driving of the positioning shaft 336 is loosened by operating the lever 337 to release the holding of the lens switching member 331 to the fixing member 332 with the positioning ball 338B. After that, the lens switching member 331 is rotated with the knob 339 so as to switch the objective lens OB1 to the objective lens OB2 and then, the positioning shaft 336 is driven again by operating the lever 337 to hold the positioning ball 338A. As a result, the objective lens OB2 is positioned.
Because the mechanism shown in FIG. 7 allows the objective lenses OB1, OB2 to move in a circular shape along the direction of the arrangement, an action upon the replacement of the objective lens and a space necessary for the replacement operation can be reduced, thereby making it possible to prevent the objective lenses OB1, OB2 from interfering with the manipulator and the like around the specimen. Further, the positioning of the lens switching member 331 is carried out not by using elasticity of a spring but by driving the positioning shaft 336, while release of the positioning can be carried out by only loosening the driving of the positioning shaft 336 without linkage with the rotation of the lens switching member 331. Thus, generation of vibration which may occur when moving the lens switching member 331 to replace the objective lens can be minimized to a possible extent.
The mechanism disclosed in the aforementioned Jpn. UM Appln. KOKAI Publication No. 6-40910 has such a problem that it is incapable of carrying out an accurate position setting due to a slight gap provided to drive the positioning shaft 336 although such an objective lens switching mechanism is demanded to execute a position setting in micron order. Then, although it can be considered to provide with a precision driving mechanism capable of eliminating such a gap, provision of a high precision driving mechanism enlarges the entire size of the positioning mechanism and increases the price of the apparatus.
Further, because upon the replacement of the objective lens, first, the driving of the positioning shaft 336 is loosened with the lever 337, the lens switching member 331 is rotated with a knob 339 to switch the objective lens and finally, the positioning shaft 336 is driven with the lever 337, it comes that the lever 337 and the knob 339 need to be operated at such two positions alternately, thereby leading to complicatedness in operation for objective lens replacement.